Currently, information handling systems are often integrated into groups with multiple users accessing and storing data. For various reasons, groups of information handling system users may be located in separate areas such as in different offices, or in different geographic locations. Even with multiple users located in separate locations the need may arise to generate a unified data storage system. For example a common database of information may be desirous, such as a customer database for a business with different geographic locations. As a result, different storage volumes may need to be maintained and integrated to store and manage data.
When common volumes of information are stored a back-up of data may be needed such as by using other data storage volumes mirroring the primary storage volume to protect the data in the case of natural disasters, data corruption or the like. Additionally, the separate user locations may need to continue to function should a disruption in communication occur between the various locations.
Should a disruption in communication occur, the storage volumes may become incoherent, and as a result a secondary, mirroring storage volume may no longer represent the data on the primary storage volume. If the primary and the secondary storage volumes no longer mirror each other the need to reestablish coherency would require the communication of the data stored on the primary volume to the secondary volume. A transmission of the primary volume to the secondary volume is undesirous due to the typically large volume of information and the time required to transmit.
Presently, to avoid the need to communicate the contents of the primary storage volume in the event of a break in communication, a bitmap is typically maintained to track the changes in the primary volume while communication between the primary and the secondary volumes is disrupted. A bitmap is utilized to provide a list of changes occurring to the primary storage volume so that the data written to the primary volume may be updated to the secondary volume when communication is reestablished. Thus, the need to transfer the entire contents of the primary storage volume to the secondary storage volume upon reestablishment of communication is eliminated. Generally, bitmaps of mirrored storage volumes are maintained in non-volatile memory to ensure their protection in the event of a power failure. Additionally, bitmaps are maintained in non-volatile memory because the mirrored storage volume system had no other method for establishing coherency besides transmitting the contents of the primary storage volume to the mirroring storage volume. Thus resulting in an input/output intensive operation.
Therefore, it would be desirable to provide a mirrored storage volume system capable of eliminating the need for a costly, time consuming non-volatilite stored bitmap system and method for ensuring the coherency of mirrored volumes or in the alternative a mirrored volume system in which a bitmap may be maintained in volatile memory.